The effect of 1-Phenyl-3-Methyl Pyrazol-5-one (HPMP) on the electrical properties of high carbon steel in Hydrochloric acid (HCI), Trioxonitrate (v) acid (HNO3) and Perchloric acid (HCIO4) was studied by weight loss method. The acidic medium caused a complete degradation of the electrical properties of the coated and uncoated high carbon steel. However, the attack was more on the uncoated coupons, which showed that HPHP is an effective corrosion inhibitor. HNO3 had the most severe effect on the metal. The coupons coated with HPMP generally had higher values of resistance (0.0155 Ω) and conductivity (6.20 mho/m) in HCI environment than the uncoated coupons (0.0043 Ω) and (1.72 mho/m). Similar results were obtained for HNO3 and HCIO4 environments. These values are lower than the values obtained for as-received coupons: -0.0466 and 8.64 mho/m respectively.
Steel is one of the most important construction metals in the world. While this is common knowledge, many people do not understand the difference between high carbon steel and other types of steel. High carbon steel is any type of steel that contains over 0.8% of carbon but less than 2.11% of carbon in its composition. It has a reputation for being especially hard, less formable and machinable, but the extra carbon makes it more brittle than the other types of steel.
High carbon steel has many advantages over other options. It is excellent for making cutting tools such as knives, saws, drill bits, farming and gardening equipment, compression springs, high ware applications, wood cutting tools and high strength wire [
The failure of steel equipment due to acid corrosion in industries is widely reported, and the use of chemical inhibitors for steel corrosion has been established to be the most practical and cost effective means of controlling corrosion [
Electrical properties of metals are usually affected when corrosion occurs. Since corrosion affects the dimensions or area of a material, one would infer that changes could occur in the electrical properties of the material due to corrosion effect. This paper reports the effect of 1-Phenyl-3-Methyl Pyrazol-5-one (HPMP) on the electrical properties of high carbon steel in various concentrations of HCI, HNO3 and HCIO4.
The high carbon steel strip was mechanically pressed cut into coupons of dimension 4.0 cm × 2.5 cm × 1.0 cm. Each coupon polished and drilled at one end, was degreased in ethanol, dried in acetone and preserved in a desiccator. Solutions were prepared using analar reagents and distilled water. The HPMP Inhibitor was synthesized as described by Vogel [
The three categories of coupons, namely: The as-received (control coupons, that were not exposed to the acid medium), coated (coupons coated with HPMP inhibitor before exposure to the acid environment) and uncoated (coupons that were exposed to the acidic medium without the HPMP inhibitor) coupons, were all subjected to the current voltage measurement before and after the weight loss experiment.
The results from
However, it was observed that the coated coupons in perchloric acid environment had higher values of weight loss than the uncoated coupons. This signifies that the inhibitor coating on the coupons was not stable and therefore dissolved, thereby aiding the corrosion of the coupons in perchloric acid. This behavior is attributed to
. Weight loss (g) of coated and uncoated coupons in 0.8 M concentration of different acid environments
Time (Days) | Weight loss (g) | |||||
---|---|---|---|---|---|---|
HCI | HNO3 | HCLO4 | ||||
Uncoated coupon | Coated coupon | Uncoated coupon | Coated coupon | Uncoated coupon | Coated coupon | |
1 | 1.3154 | 1.1484 | 0.6189 | 0.4594 | 1.0085 | 1.0003 |
2 | 1.5076 | 1.3224 | 0.7795 | 0.5847 | 1.0216 | 1.0262 |
3 | 1.5146 | 1.3557 | 1.0785 | 0.8338 | 1.0340 | 1.0460 |
4 | 1.5309 | 1.4266 | 1.2789 | 1.0353 | 1.0430 | 1.0920 |
5 | 1.5481 | 1.4697 | 1.5319 | 1.3353 | 1.0516 | 1.1482 |
6 | 1.5645 | 1.4890 | 1.6746 | 1.5202 | 1.0689 | 1.1847 |
7 | 1.5767 | 1.5098 | 1.8565 | 1.8009 | 1.0768 | 1.1963 |
the fact that perchloric acid is one of the strongest acids known [
Like all metals, steel can conduct electricity. The three main electrical properties of steel include its electrical conductivity, electrical resistivity and temperature co-efficient. Electrical conductivity is the ability of a material to conduct an electrical charge over a certain distance, while resistivity is the reciprocal of conductivity. The I-V characteristics of high carbon steel in different concentrations of the acidic medium are shown on
Although there was a remarkable decrease in the I-V characteristics of the coupons exposed to the acid environment, the normal Ohmic behavior, which is usually associated with metallic conductors still maintained. That is, the exposed coupons were observed to exhibit the normal linearity variation pattern typical of electrical conducting materials as shown in
. Both parameters were seen to decrease with increasing concentration. This result is in agreement with earlier researchers [13] [15] . Table 4 shows the resistance and conductivity of the coated and uncoated coupons in th
I-V Characteristic of high carbon steel coupons in HCl, HNO3, HClO4
. I-V characteristics of high carbon steel coupons in HCl, HNO3 and HCIO4
Voltage (mV) | Current (A) | ||||||
---|---|---|---|---|---|---|---|
As Received coupons | HCl | HNO3 | HClO4 | ||||
Uncoated coupons | Coated coupons | Uncoated coupons | Coated coupons | Uncoated coupons | Coated coupons | ||
2 | 0.14 | 0.00 | 0.05 | 0.00 | 0.00 | 0.02 | 0.02 |
4 | 0.22 | 0.02 | 0.07 | 0.00 | 0.02 | 0.03 | 0.05 |
6 | 0.32 | 0.03 | 0.10 | 0.01 | 0.03 | 0.05 | 0.07 |
8 | 0.41 | 0.03 | 0.15 | 0.01 | 0.05 | 0.07 | 0.10 |
10 | 0.50 | 0.05 | 0.17 | 0.02 | 0.07 | 0.07 | 0.10 |
12 | 0.60 | 0.05 | 0.20 | 0.02 | 0.10 | 0.10 | 0.12 |
14 | 0.69 | 0.05 | 0.22 | 0.03 | 0.10 | 0.10 | 0.15 |
16 | 0.79 | 0.07 | 0.27 | 0.03 | 0.13 | 0.12 | 0.20 |
. Resistance (Ω) and conductivity (mho/m) of coupons in various concentrations of the acids
Sample | Conc. (M) | ACID | |||||
---|---|---|---|---|---|---|---|
HCl | HNO3 | HClO4 | |||||
R (Ω) | K × 10−3 (mho/m) | R (Ω) | K × 10−3 | R (Ω) | K × 10−3 (mho/m) | ||
0.3 | 0.0444 | 17.76 | 0.0068 | 2.72 | 0.0203 | 8.12 | |
0.5 | 0.0372 | 14.88 | 0.0030 | 1.20 | 0.0104 | 4.16 | |
0.8 | 0.0323 | 12.92 | 0.0012 | 0.48 | 0.0157 | 6.28 | |
1.0 | 0.0308 | 12.32 | 0.0009 | 0.36 | 0.0130 | 5.20 | |
1.5 | 0.0259 | 10.36 | - | - | 0.0057 | 2.28 | |
2.0 | 0.0200 | 8.00 | - | - | - | - |
. Resistance (Ω) and Conductivity (mho/m) of coupons in the various acids
Sample | Nature of Coupon | Acid | Resistance (Ω) | Cond. (mho/m) (×10−3) |
---|---|---|---|---|
As-Received | - | 0.0466 | 18.64 | |
Uncoated | HCl | 0.0043 | 1.72 | |
Coated | HCl | 0.0155 | 6.20 | |
Uncoated | HNO3 | 0.0024 | 0.96 | |
Coated | HNO3 | 0.0092 | 3.68 | |
Uncoated | HClO4 | 0.0071 | 2.84 | |
Coated | HClO4 | 0.0114 | 4.56 |
various acidic media. The conductivities of both the uncoated and coated coupons showed a remarkable deviation from those of the as-received samples.
This observation could be explained in terms of the dimensional changes which occurred during the corrosion process which in turn affects the properties of the metal. Similar observations were reported by Dawson and Turner [
Based on the experimental results, it has been proven that HPMP is an effective inhibitor for high carbon steel in HCI, HNO3 and HClO4 since it was able to protect the metal from the direct attack of the acids. This is evidenced by the higher conductivity values (which means lower resistivity values) recorded for the coated samples other than the samples not coated with HPMP.